Field of the Invention
The present invention relates to a method for manufacturing a silicon carbide semiconductor device, and a silicon carbide semiconductor device.
Description of the Background Art
Generally in a power semiconductor device (power device), a drift layer having a low impurity concentration and a large thickness ensures a breakdown voltage of the device. However, in this configuration, in order to reduce an on-resistance of the device, the impurity concentration must be increased in the drift layer, or the thickness of the drift layer must be decreased. In other words, as long as relying on the impurity concentration and thickness of the drift layer, the on-resistance and breakdown voltage of the device are in a trade-off relationship.
In order to overcome such a trade-off relationship, a superjunction structure (for example, refer to Jpn. J. Appl. Phys. Vol. 36 (1997) pp. 6254-6262) has been proposed for a power semiconductor device using silicon (Si). Originally, silicon carbide (SiC) is a material exhibiting a lower loss and higher breakdown voltage than Si. However, if further improvement in characteristics is sought, it can be considered to employ the superjunction structure also in the power semiconductor device using SiC (for example, refer to Japanese Patent Laying-Open No. 2001-144292).